Effects of Accelerated Aging Tests on Some Bending Properties of Hardwood Composite Panels

There is a lack of information on the effects of accelerated aging tests or severe weather exposure on hardwood reconstituted structural composite panels. This study found that 13 of the 16 composites had average modulus of rupture (MOR) and modulus of elasticity (MOE) values greater than those of the commercial Douglas-fir plywood at controlled or unexposed condition. The ranking of effects of various exposure tests on bending values of composites according to their severity in an increasing order was 1) 24-hour soak, 2) 1-hour boil, 3) 2-hour boil, 4) ASTM-6 cycles, and 5) WCAA-6 cycles. The strength reduction due to exposure tests on hardwood composites was attributed to low density as a result of thickness swelling. Both ASTM and WCAA tests had similar influences on all properties. Both 4-cycle and 6-cycle tests obtained from these two ASTM and WCAA cyclic methods resulted in about the same degree of bending strength reduction on tested panels. There was no real strength value difference between two kinds (dry and wet) of glueline used in veneered panels. The 1/2-inch red oak or hard maple veneered exterior particleboard composite had bending strength retentions approaching those of plywood. Composite panels with a total thickness of I/2-inch appeared to have better strength retention and less thickness swelling than those panels with 3/4-inch thickness. The overall average strength retentions of MOR, and MOE, properties following accelerated aging treatments, were about 40 to 50 percent, respectively, of those of the control specimens. Further efforts to improve the performance of hardwood composite panels are needed.

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